1. Field of the Invention
This invention relates to rolling doors and more particularly to rolling fire doors having controls for holding such doors open and for automatically initiating the closing of such doors.
2. Description of the Prior Art
Rolling doors, and more particularly, rolling steel doors, are utilized to provide security and protection in commercial, institutional and industrial buildings. A typical rolling door includes a curtain positioned between a pair of vertical guides on opposite sides of an opening. The curtain is moveable upward in the guides to enable passage through the opening and is moveable downward to seal the opening and prevent passage therethrough.
A typical curtain includes a plurality of horizontally disposed slats pivotally interconnected together along their sides and having their opposite ends received in the guides positioned on the opposite sides of the opening. The bottom of the curtain typically has a bottom bar that may include a handle to permit the curtain to be manually opened. The top of the curtain is preferably connected to a shaft which is positioned above the guides. The shaft is rotatable around its longitudinal axis relative to a rigid support. A spring connected between the shaft and the rigid support applies to the shaft a torque that counterbalances at least a part of the weight of the door.
A rolling door may be moved to the open position by applying a lifting force to the handle of the bottom bar. When opened, the rolling door coils around the shaft until the weight of the door between the guides is insufficient to overcome the spring tension applied to the shaft. In another embodiment, a rotational torque is applied to a gear at one end of the shaft to cause the shaft to rotate thereby coiling the door thereabout. This rotational torque may be applied by an electric motor or by manually pulling a chain connected around the gear, as is known in the art.
When used as a fire door, these rolling doors must be returnable to their closed position under certain alarm conditions. To this end, prior art rolling fire doors include a release latch which secures the torque of the spring against the shaft. In response to a suitable alarm, such as a fire alarm, the release latch disengages from the spring and releases all or a part of the torque of the spring on the shaft. In the absence of torque on the shaft, the weight of the door causes the door to close.
A problem with the release latch, however, is that once released, the spring must be manually retorqued against the shaft and the release latch reengaged. This manual retorquing of the spring and reengaging of the release latch is time-intensive and potentially dangerous. Moreover, the time to retorque the spring around the shaft and reengage the release latch is a disincentive to testing the operation of the release latch on the spring.
It is therefore an object of the present invention to provide a rolling door hold-open/release system which overcomes these drawbacks of the prior art. It is an object of the present invention to provide a rolling door that has a door hold-open/release system which enables the rolling door to be lowered to a closed position without releasing tension on a spring. It is an object of the present invention to provide a delayed closing of a rolling door in response to detecting an over-temperature, alarm or power-out condition. It is an object of the present invention to provide a door hold-open/release system which retains a vertically-openable door, such as a rolling door, open and which enables closing of the door or delayed closing of the door in response to detecting a temperature in excess of a desired temperature, activation of an external alarm or activation of a test switch.